METEOEOLOGICAL PEEIODICITT. 173 



Dr. Weiss of Vienna, says : — " Cosmical clouds undoubtedly 

 appear in the universe, but only of such density that in most 

 cases they possess sufficient coherence to withstand the des- 

 tructive operation of the sun's attraction, not only up to the 

 boundariCis ot our system, but even within it." 



He considers that comets from these clouds, when the earth 

 meets them, give ocular demonstration of the fact in a shower of 

 meteors ; and on the 27th of November, 1872, when the earth 

 passed over the orbit of Biela's comet, such a shower actually 

 took place, and a magnificent display of meteors was seen. At 

 Turin, 33,400 were observed in 6^ hours ; and in other places 

 similar displays were seen ; and if to these recorded meteors we 

 add the far greater number that were not seen, we get some idea 

 of the density of this stream representing only a faint comet, and 

 how potent a cause for effects on terrestrial temperature may 

 exist between the earth and the sun, all unheeded by us. 



I confess that the account given of the darkening and red 

 colour of the sun during a whole year does not seem to me so 

 incredible as many have esteemed it ; for we have in modern 

 times two accounts of a similar phenomenon, lasting for weeks, 

 viz., the dry fogs of 1783 and 1831. Many have attributed these 

 to the action of volcanoes, and it is well known that in 1783 the 

 fearful earthquakes in Calabria took place in February, and 

 began a long list of volcanic eruption in the world ; but in esti- 

 mating the part played by volcanoes in these and similar 

 phenomena, it is to be borne in mind that there must be a cause 

 for the volcanic outbreak, and probably a cosmical one. Modern 

 research has shown that they are subject to tidal effects like the 

 ocean, or to distant attractive forces, and that eruptions are not 

 caused by contraction of the earth's surface only^ but by this and 

 some other forces combined. 



Besides, if great volcanic eruptions produced these dry fogs, 

 we should have had many recorded in the world's history, and the 

 peculiar and disagreeable smell would have been recognised ; 

 probably, also, rain would have thrown them down. 



On the other hand, dust has been collected on the high snow- 

 covered mountains, and when examined it proved to be meteoric 

 dust. 



Of the dry fog which came on suddenly in June, 1873, it is 

 recorded that it extended from the northern coasts of Africa, over 

 France, to Sweden, and over great part of North America, and 

 lasted more than a month. Travellers found it on the summits of 

 the Alps. Abundant rains in June and July, and most violent 

 winds did not dissipate it ; and, in some places, it was so dense 

 that the sun could not be seen until it had attained an altitude 

 of twelve degrees, and throughout the daytime it was red and so 

 dull that it might be looked at with the naked eye. The fog 



